The lowest (i.e. threshold) nicotine dose in cigarettes that produces tobacco reinforcement and dependence is almost certainly not lower than the threshold dose for discrimination of nicotine's interoceptive stimulus effects from smoking. Despite a half century of animal research on nicotine discrimination and prior human studies of threshold dose for discriminating drugs other than nicotine, no research has clearly assessed this nicotine discrimination threshold in humans via cigarettes because of difficulty controlling nicotine dosing with tobacco intake. Because our lab has, by far, the most experience assessing nicotine discrimination in humans (including threshold dose, with a nicotine formulation other than tobacco), we propose to employ well- validated behavioral discrimination methodology to identify the cigarette nicotine threshold dose for discrimination using nicotine research cigarette (NRC) from the NIDA Drug Supply Program. We will assess threshold doses in a diverse sample of 100 healthy male and female smokers varying in dependence level and menthol preference to generate evidence that informs policy on establishing a maximum nicotine content in tobacco cigarettes that could prevent the onset and maintenance of dependence. We hypothesize that this nicotine threshold dose for discrimination will be lower than the yield of most current commercial brands, which typically exceed 0.4 mg. We also hypothesize that the threshold dose will be lower in nondependent vs. dependent smokers, in men vs. women, and perhaps as a function of cigarette menthol preference, consistent with prior research on differences in nicotine sensitivity. Importantly, this study will also separately assess self-administration of nicotine from these cigarettes to determine the relationship between nicotine discrimination threshold dose and reinforcement threshold dose in smoking. This research is highly significant because limiting nicotine cigarettes to amounts below this threshold dose could minimize risk of nondependent smokers escalating to dependence and make it easier for dependent smokers to quit smoking. As such, this R21 addresses key research objectives of the FDA's Center for Tobacco Products (CTP), notably those involving reducing addiction to tobacco products by modifying nicotine levels, including in potentially vulnerable populations, and adverse health consequences of tobacco use.